The invention relates generally to the field of printing using a raster printer, and more specifically to the field of high resolution printing of text using such printers. As used herein, raster printers include, but are not necessarily limited to, laser, ink jet, and light emitting diode printers.
In the typesetting industry today, the highest quality of typesetting is phototypesetting. Phototypesetting is accomplished by passing a beam of light through a photographic negative of a particular font and creating an image on a photosensitive medium. This method provides the sharpest resolution. Resolution is defined as the roughness or sharpness of the edges of the printed object, such as a letter of the alphabet.
Laser typesetting, which has slightly lower resolution, tries to mimic phototypesetting as closely as possible. Laser typesetting devices project a series of dots to form a given letter. The resolution of laser typesetting, as seen by the edge of the letters produced, is roughly proportional to the number of dots per square inch the laser can provide.
Laser printers currently available to the home computing consumer as well as to the commercial consumer typically have a resolution of 300 dots per linear inch (90,000 dots per square inch). This resolution is more than sufficient to create a "letter quality" document, but "stair-stepping" at the letter edges is unacceptable to publishers of higher than "letter quality" documents, such as book and magazine publishers, as well as advertisers.
Not all laser printers are unacceptable for high quality work. Publishers and advertisers prefer phototypeset originals for their publications, but will accept as "camera-ready," originals created by laser printers of a quality of 1200 dots per linear inch. These 1200 dot per linear inch laser printers, however, are currently more than ten times as expensive as the 300 dot per linear inch laser printers They are thus only economically feasible for large-quantity print shops, not for a small business using a personal computer for word processing.
Presently, one wishing to use laser typesetting for word processing originals prior to delivery to a publisher must find a print shop with both a 1200 dot per linear inch laser printer and compatible word processing computer equipment. Most print shops either have no laser printer or have a 300 dot per linear inch laser printer. In addition, the process of creating camera-ready 1200 dot per linear inch originals is so slow that many print shops using such printers also use a 300 dot per linear inch printer for proofing.
It is therefore an object of the present invention to provide a method for increasing the resolution of images produced by conventional, lower resolution raster printers.
It is another object of the invention to provide a method for producing high resolution documents using a 300 dot per linear inch laser printer.
Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will be obvious from that description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by the methods and apparatus particularly pointed out in the appended claims.